   (assoc app-initial-model ::debugger
                            {:initial-model              app-initial-model
 
-                            :signal-events              (list)
+                            :signal-events              nil
                             :next-signal-id             0
 
-                            :action-events              (list)
+                            :action-events              nil
                             :next-action-id             0
 
                             :persist?                   false

           (as-> model m
                 (update-in m [::debugger :action-events] #(filter :enabled? %))
                 (update-in m [::debugger :signal-events] #(remove (partial -orphaned-signal? m) %)))

           ::toggle-visibility
           (update-in model [::debugger :visible?] not)

                                  :on-change #(dispatch ::on-toggle-persist)}]
   [:label {:for "persist-toggle"} "Persist session"]
   [-menu-button "Sweep" #(dispatch ::on-sweep) "Removes disabled actions and \"orphaned\" signals from history"]
   [-menu-button "Sweep All" #(dispatch ::on-sweep-all) "Clears debugger history without affecting app model"]
   [-menu-button "Reset" #(dispatch ::on-reset) "Removes all actions and signals resetting the model to initial state"]
   [-menu-button
    (str "Hide (" toggle-visibility-shortcut ")")
